1. Field of the Invention:
The present invention relates to a system for controlling a high-power ion beam such as for ion implanters, and, more particularly, to steering, measuring, and/or dissipating the power of the high-power ion beam, and an associated magnetic beam steering system.
2. Description of the Related Art:
Ion implantation is a materials engineering process by which ions of a material are accelerated in an electrical field and impacted into a solid. This process is used to change the physical, chemical, or electrical properties of the solid. Ion implantation is often used in semiconductor device fabrication and in metal finishing, as well as various applications in materials science. Ion implantation equipment typically consists of an ion source, where ions of the desired element are produced, an accelerator, where the ions are electrostatically accelerated to a high energy, and a target chamber, where the ions impinge on a target, which is the material to be implanted. The energy of the ions, as well as the ion species and the composition of the target, determine the depth of penetration of the ions in the solid, i.e., the “range” of the ions.
There are various uses for ion implantation, such as the introduction of dopants (e.g., boron, phosphorus or arsenic) into a semiconductor material such as silicon. Another use for ion implantation is for cleaving (exfoliating) thin sheets (lamina) of hard crystalline materials such as silicon, sapphire, etc. Generally, this process involves implanting light ions into the material where they will stop below the surface in a layer. The material may then be heated (for example), causing the material above the implanted layer to cleave off or exfoliate in a sheet or lamina.
A proton accelerator is an example ion beam source that produces ion beams. In some instances, such ion beams have power intensities of about 100 kW, and may have sizes of approximately 10 mm in diameter. In general, it is not possible to handle this power density with a stationary water-cooled or radiation-cooled surface, particularly when dissipating or “dumping” the beam's power. The problem is generally solved by dissipating the power over a larger area. In one arrangement, this can be accomplished by rotating the target upon which the ion beam strikes, such as a large disk or drum, so no one portion of the target absorbs the full power of the ion beam. For example, the target in a typical beam dump system may have a diameter of approximately 2 m or greater, which rotates at approximately 100 rpm or greater, thus spreading the power dissipation over a large area. An alternative approach is to scan the beam over a larger area—that is, moving the beam over the target instead of moving the target.
The current systems for controlling high-power ion beams, particularly to dissipate the power of the beam during a beam dump, are large and bulky, expensive, and don't provide any function other than to absorb the ion beam's power.